The progressive reduction in feature size in integrated circuits (ICs) is driven in part by advances in lithography. ICs may be created by alternately etching material away from a chip and depositing material on the chip. Each layer of materials etched from the chip may be defined by a lithographic process in which light shines through or reflected from a mask, exposing a photosensitive material, e.g., a photoresist after imaging through projection optics.
The ability to focus the light used in lithography, and hence to produce increasingly smaller line widths in ICs, is a function of the wavelength of the light used. Current techniques may use light having a wavelength of about 193 nm. The use of “soft” x-rays (wavelength range of λ≈10 nm to 20 nm) in lithography is being explored to achieve smaller desired feature sizes. Soft x-ray radiation may also be referred to as extreme ultraviolet (EUV) radiation.